Method of and apparatus for withdrawing lowermost sheets from stacks



atent Dec. m42

METHOD 0F 't STAGES lr' APPARATUS FOR DRAWING WERMOS'E SHEE'S F Vincent E. eywood and George A. Anderson.

orcester, Mass., assignors to States Envelope Company, Sprineld, Mass., a corporation or ine Application March 312, 1940, Serial No. 323,514 a calms. (ci. eri-fn The lpresent invention relates to an improved method of and apparatus for accomplishing the separate withdrawal of the lowermost sheet from a stack of nat sheets or blanks, such as is frequently employed in connection with envelope machines, or other mechanisms for the performance of various operations on a sheet.

-When the lowermost sheet is withdrawn from a stack, certain difculties arise, owing to the fact that the weight of the entire stack bears on the sheet being withdrawn, and thus creates a vfriction between sheets tending to cause the simultaneous withdrawal of more than one sheet. This tendency for sheets to adhere to each other is still further increased when thel sheets being handled are composed of paper having a rough finish;

In order to overcome the eiect of friction between the lowermostr sheet and the remainder of the stack lying above it, it has heretofore been proposed to blow air under pressure at one or more places beneath the stack, to free the lowermost sheet lby vibrating the same, as disclosed in Patent No. 1,942,527, issued January 9, i934. While the aforementioned use of air pressure in facilitating the withdrawal of a lowermost sheet is eective when the sheets are composed of relatively thin smooth surfaced material, the desired results cannot be obtained when the stack is composed of very rough iinished sheets, due to the inability of air pressure alone to overcome the tendency for the sheets to adhere to each other. Furthermore, when' the stack is composed of .punctured sheets, such as are employed in the manufacture of window envelopes, air under pressure is entirely ineiective, since it will blow through the stack.

According to the present invention, there is provided an improved method of and apparatus forv withdrawing the lowermost sheet from a stack, characterized by the positive separation of the lowermostsheet from the stack at both its leading and trailing edges, preparatory to withdrawal. Furthermore, the actualwithdrawal of the lowermost sheet is accompanied by the operation of means for positively holding the second lowermost sheet against withdrawal, thereby eliminating any possibility of the' previously separated sheet pulling another sheet with it as it is withdrawn. The above and other advantageous features of the invention will hereinafter -low shaft 5, adapted to be connected at predeter- Fig. l is a plan View of sheet-withdrawing paratus embodying the invention.

' Fig. 2 is a vertical sectlonalview along the line 2 2 of Fig. l.

Figs. 3 and 4 are sectional views similar to Fig. 2, illustrating the steps in the separation and withdrawal of the iowermost sheet.

Fig, 5 is a fragmentary plan view of the sheetgripping device.

In the illustrative embodiment of the invention shown in the drawing, the sheet-withdrawing apparatus is shown in connection with a stack of sheets i supported on an inclined stack plate 2, in cooperation with stops 3, although a hori- 'zontal stack plate may be used, if desired. While the sheets l are shown in Fig. 1 as being in the form of envelope blanks having window openings at lo, obviously, the sheet-withdrawing apparatus, hereinafter described, -may be also used in connection with sheets or blanks for other pur- DOSES.

'A portion of the stack of sheets I projects beyond the upper edge of the stack plate 2, so that the under side of the lowermost sheet l can be engaged by a sucker d turnable about a holmined intervals to a suitable source of suction, not shown. In operation,I the suckerA t is adapted to engage and grip the underside of the lowermost sheet adjacent to its leading edge and to bend it over a roll t intola position in which it inFig. d.

.a portion of the stack also extends beyond the lower e or the stack plate 2, so that the under side of the lowermost sheet l can be operated upon by a second sucker turnable about a hollow shaft it to engage the lowermost sheet adjacent to its trailing edge. The shaft l0 is adapted to be connected at predetermined intervals to ble source of suction, not shown, and is operated in timed relation with the erst shaft s,

so that the suckers@ and 9 are adapted to simultaneously engage and grip the lowermost t adjacent both its leading and trailing edges.

Therefore, es the leading edge of the lowermost sheet is seperated irons the stock hy the sooner its trailing edge is els@ senareted from the sisch by the sucker ii, es shown in Fig. 3, so that the lovvermost sheet is positively seperated rom the steci: et opposite ends in edvance of its with droivel movement hy the segments il.

Thai; portion. of the stools edjecent to the sucker s is also opereted noon hy e gripper ii pivot` aiiy mounted on e. shaft i2. is best shown in the erioner ii is forked, so es provide pins i3 on opposite sides of the Sucher ii, adopted to engage extreme end of the stock, Without mtererenee with the sucker d. move- :rnent ci the gripper shet i2 is so timed et es soon es the sucker seno-rates the trailing edge of lowermost sh et from the stesi; by nesting into the 'h the position oi Fig. 3, steels. rEhis turni is sudcient to site, f hit the end ci? the stock: sway from the s; es ence gersted seele, so that the pins i3 ere very positively engaged with the end ori sheet next shove the lowermost eedy been seperated from steels, prenemtory to its withdrawal.

With the peri-s oconnying position oi Fig. 3, it is obvious then that continued rotation of the segments i :from the position shoe-Jn, insult in seizure of the leading edge o the lowermost sheet 'the segments Di ond roll ii and its withdrewni rom the stach, es indicated in Fig. 4, et which time suction is removed from the suckers l end Since the sheet ext shove the Sheet 'being Withdrawn is then goositively held by the gripper i3, it is obvious thst the withdrevel oi' the iowerinost sheet is accomplished without any possihiiity oi the sheet next shove rvithdr i simultaneously. This result ie-siding end from the end the tTA e sheet next shove hy f i o eotnsi. mcveme 'Y- oi nithdmirroi hy the segments i. Therefore', even 'though the sheets .h ve such oiigh es to exhibit e. strong tendency to ere to each othenthis iriotionel engogemen is hrotlsen and entirely overcome, due to the feet that hy the time the lowermost sheet ste-rtsis wihdrsvfoi movement, the sh next above hss elses-dy eenereted there s, and in ne dition, hos he mcvem Enom the for present invention. i'

is provided on improved method of snol crews ior accomplishing the diie to simniten'eons porting;

osos-,ive

seperate Withdrawal of the lower-most sheet from e, stoel: oiiiat sheets or blanks, without possibile ity of the sheet next above being simultoneou'sly withdrawn, even when the sheets ere'composed of materiel having a. rough surioce such as to cause e. noturel adhesion between, the sheets.

We claim:

i. A method oi withdrawing the lowermost sheet from a stock. of dat sheets, characterized by the positive separation of the lowermost sheet from the stack at both its leading and trailing edges, preparatory to Withdrawal of the sepa,- roted sheet, followed by positive engagement of the nextlovfermost sheet to prevent its movement in the stack during Withdrawal of the pre viousiy seperated lowermost sheet.

2. Apparatus for withdrawing the lowermost sheet from e, stack of not iiexible sheets comprising s. supporting member for the stach, suction-operated elements for engaging and defiecting opposite edges of the lower-most sheet away from the stack beyond the ends of ythe supporting member, withdrawing means operable upon e deiected edge of the lowermost sheet, and gripping means engageable with the next lowermost sheet, in advance of the operation of said withdrawing means, to hold it positively against the remainder ci the stack during the operation of seid withdrawing means.

3. Apparatus for withdrawing the lowermost sheet from e. steel; of flot iiexible sheets com--l prisme e supporting member for the steels, plv otally mounted suckers engageoble with oDDOste edges o the lowerrnost sheet which entend be-` yond said supporting member to fies: sold sheet sway from the stack, withdrawing means enge'geoble with e deflected portion o the lowerrnost sheet and s. pivote-ily monnted gripper engageable with the next lowermost sheet, in advence of the operation o' withdrawing means, hold it positie/eli7 the remainder of the stack during of seid Withtvine ineens on the 'im ost sheet.

e. ltipps,rettus ior withdrsvnng the lowermost niece from a. sta-ck or comprising e, supmember for the stack, withdrawing means, means for positively separating the lowermost piece from the steelt beyond opposite ende y of said member in advance of operation of said 

